BSc (Hons) Computer Science. with Network Security. Examinations for / Semester 2

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BSc (Hons) Computer Science with Network Security Cohort: BCNS/14/FT Examinations for 2015-2016 / Semester 2 MODULE: Image Processing and Computer Vision MODULE CODE: SCG 5104C Duration: 2 Hours 30

1 BSc (Hons) Computer Science with Network Security Cohort: BCNS/14/FT Examinations for / Semester 2 MODULE: Image Processing and Computer Vision MODULE CODE: SCG 5104C Duration: 2 Hours 30 Minutes Instructions to Candidates: 1. Answer all FOUR questions. 2. Questions may be answered in any order but your answers must show the question number clearly. 3. Always start a new question on a fresh page. 4. All questions do not carry equal marks. 5. Total marks 100. This Exam paper contains 4 questions and 7 pages. Page 1 of 7

2 ANSWER ALL QUESTIONS QUESTION 1: (25 MARKS) The visual significance of individual pixel bits in an image can be assessed in a subjective but useful manner by the technique of bit-plane slicing. i. Explain the concept of bit-plane slicing. ii. iii. Using MATLAB codes, explain how bit-plane slicing is achieved. Using MATLAB codes, explain how image reconstruction using n-bit planes is carried out. (2+3+3 marks) The main barrier to effective image processing and signal processing in general is noise. i. What is noise in digital images? ii. iii. Explain four sources from which digital noise may originate. Explain why Median Filtering is appropriate for salt and pepper noise removal. (2+4+2 marks) MATLAB is widely used in digital image processing. The following is an extract of a MATLAB code as applied to image D. Explain each line of code. D=imread( onion.png ); Dred1=D(:,:,1); Dgreen1=D(:,:,2); Dblue1=4D(:,:,3); subplot(2,2,1); imshow(d); axis image; subplot(2,2,2); imshow(dred); title( red ); subplot(2,2,3); imshow(dgreen); title( green ); subplot(2,2,4); imshow(dblue); title( blue ); Page 2 of 7

3 (d) Thresholding is a basic point transform operation. With the help of an algorithm explain the concept of Thresholding. (e) Converting an analog signal into a digital signal requires two basic steps; Sampling and Quantisation. Differentiate between Sampling and Quantisation. QUESTION 2: (25 MARKS) There are two broad categories of image enhancement techniques; Spatial domain techniques and Frequency domain techniques. Distinguish between these two techniques. The three basic types of functions (transformation) that are frequently used in image enhancement are Linear, Logarithmic and Power Law. The transformation map plot below depicts various curves that fall under these three types of enhancement techniques. i) With reference to the transformation map plot shown above, explain the following transformation as applied to image enhancement. Page 3 of 7

Figure 1 Figure 2 (4 marks) Basic arithmetic operations can be performed quickly and easily on image pixels for a variety of

4 a. Linear b. Logarithmic c. Power-Law (6 marks) ii) Explain how the Power Law when applied to Figure 1 and Figure 2 below may improve the images. Figure 1 Figure 2 (4 marks) Basic arithmetic operations can be performed quickly and easily on image pixels for a variety of effects and applications. With the help of an example explain one such application. (2 marks) (d) i) Explain what you understand by Histogram Equalisation. (2 marks) ii) Explain why images cannot be reconstructed from histograms. (2 marks) Page 4 of 7

5 iii) The table below shows the intensity distribution of a 3-bit image (L=8) of size 64 x 64 (MN =4096). Perform histogram equalization to transform it into a histogram equalised image. where r k is the k th intensity value and n k is the number of pixels in the image with intensity r k (6 marks) QUESTION 3: (30 MARKS) i) Give detailed explanation on each of the following. Support your answer with diagrams. a. Erosion b. Dilation c. Closing d. Opening e. HIT Transformation f. MISS Transformation ( marks) Page 5 of 7

ii) The edge of the image in Figure below needs to be cleared such that the image in Figure is obtained. As a result, your advice is sought to propose a morphological procedure to achieve this.

6 ii) The edge of the image in Figure below needs to be cleared such that the image in Figure is obtained. As a result, your advice is sought to propose a morphological procedure to achieve this. You need to specify the structuring element(s) that you would use in your procedure. A 4 x 4 gray-scale original image f (x, y) is given below: f (x, y) = Compute the filtered output images after passing through the spatial linear filter as specified by the mask w 1 (by using zero-padding of the original image). (10 marks) A 4 x 4 gray-scale image is given as follows: Filter the image with a 3x3 median filter, after zero padding. Page 6 of 7

7 QUESTION 4: (20 MARKS) The Prewitt Operator is used for edge detection in an image. Explain how Horizontal and Vertical edges are detected using this type of operator. Explain with valid reason which one of the following two is applied on images; the Fourier series or the Fourier Transform. Huffman Encoding is a text compression technique. i) Explain the concept underlying the Huffman codes. ii) Create a Huffman tree and Huffman table for the word COMMITTEE. The table should show the code word for each symbol and the corresponding code-word length. iii) Given the following Huffman codes, encode the string toad. Huffman Code Character 00 a 01 o 10 t 110 d 1110 g 1111 c (4+4+2 marks) ***END OF QUESTION PAPER*** Page 7 of 7

Babu Madhav Institute of Information Technology Years Integrated M.Sc.(IT)(Semester - 7)

Babu Madhav Institute of Information Technology Years Integrated M.Sc.(IT)(Semester - 7) 5 Years Integrated M.Sc.(IT)(Semester - 7) 060010707 Digital Image Processing UNIT 1 Introduction to Image Processing Q: 1 Answer in short. 1. What is digital image? 1. Define pixel or picture element?